package sma.gmap;
/*
 * Originally written by Andrew Rowbottom. 
 * Released freely into the public domain, use it how you want, don't blame me.
 * No warranty for this code is taken in any way. 
 */

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;

import java.text.DecimalFormat;

/**
 * A utility class to assist in encoding and decoding google tile references
 *
 * For reasons of my own longitude is treated as being between -180 and +180
 * and internally latitude is treated as being from -1 to +1 and then converted to a mercator projection
 * before return.
 *
 * All rectangles are sorted so the width and height are +ve
 */
public class GoogleTileUtils {
   /**
    * hidden constructor, this is a Utils class
    */
   private GoogleTileUtils() {
      super();
   }

  
   /** Returns a buffered image with the corner lat/lon,keyhole id and zoom level written on it.
    * @param keyholeString the keyhole string to return the image for.
    * @return 
    */
   public static BufferedImage getDebugTileFor(String keyholeString) {
      BufferedImage img = new BufferedImage(256, 256, BufferedImage.TYPE_INT_RGB);
      Graphics g        = img.getGraphics();
      g.setColor(Color.gray);
      g.fillRect(0, 0, 256, 256);
      g.setColor(Color.black);

      int scale = 400 / keyholeString.length();
      g.setFont(new Font("Serif", Font.BOLD, scale));
      g.drawString(keyholeString + " (z=" + getTileZoom(keyholeString) + ")", 10, 200);

      Rectangle2D r    = getLatLong(keyholeString);
      DecimalFormat df = new DecimalFormat("#.####");
      g.setFont(new Font("SanSerif", 0, 15));

      g.drawString(df.format(r.getMinY()) + "," + df.format(r.getMinX()) + " (w:" + df.format(r.getWidth())+" h:" + df.format(r.getHeight())+ ")", 10, 250);
      g.drawString(df.format(r.getMaxY()) + "," + df.format(r.getMaxX()), 150, 20);
      g.drawRect(1, 1, 255, 255);
      g.dispose();

      return img;
   }

   /** Returns a buffered image with the corner lat/lon,x,y and zoom level written on it.
   */
   public static BufferedImage getDebugTileFor(int x, int y, int zoom) {
      BufferedImage img = new BufferedImage(256, 256, BufferedImage.TYPE_INT_RGB);
      Graphics g        = img.getGraphics();
      g.setColor(Color.gray);
      g.fillRect(0, 0, 256, 256);
      g.setColor(Color.black);

      int scale = 20;
      g.setFont(new Font("Serif", Font.BOLD, scale));
      g.drawString("x:" + x + " y:" + y + " z:" + zoom, 10, 200);

      Rectangle2D r    = getLatLong(x, y, zoom);
      DecimalFormat df = new DecimalFormat("#.####");
      g.setFont(new Font("SanSerif", 0, 15));

      g.drawString(df.format(r.getMinY()) + "," + df.format(r.getMinX())+ " (w:" + df.format(r.getWidth())+" h:" + df.format(r.getHeight())+ ")", 10, 250);
      g.drawString(df.format(r.getMaxY()) + "," + df.format(r.getMaxX()), 150, 20);
      g.drawRect(1, 1, 255, 255);
      g.dispose();

      return img;
   }

   /**
    * returns a Rectangle2D with x = lon, y = lat, width=lonSpan, height=latSpan for a keyhole string.
    */
   public static Rectangle2D.Double getLatLong(String keyholeStr) {
      // must start with "t"
      if ((keyholeStr == null) || (keyholeStr.length() == 0) || (keyholeStr.charAt(0) != 't')) {
         throw new RuntimeException("Keyhole string must start with 't'");
      }

      double lon      = -180; // x
      double lonWidth = 360; // width 360

      //double lat = -90;  // y
      //double latHeight = 180; // height 180
      double lat       = -1;
      double latHeight = 2;

      for (int i = 1; i < keyholeStr.length(); i++) {
         lonWidth /= 2;
         latHeight /= 2;

         char c = keyholeStr.charAt(i);

         switch (c) {
            case 's':

               // lat += latHeight;
               lon += lonWidth;

               break;

            case 'r':
               lat += latHeight;
               lon += lonWidth;

               break;

            case 'q':
               lat += latHeight;

               // lon += lonWidth;
               break;

            case 't':

               //lat += latHeight;
               //lon += lonWidth;
               break;

            default:
               throw new RuntimeException("unknown char '" + c + "' when decoding keyhole string.");
         }
      }

      // convert lat and latHeight to degrees in a transverse mercator projection
      // note that in fact the coordinates go from about -85 to +85 not -90 to 90!
      latHeight += lat;
      latHeight = (2 * Math.atan(Math.exp(Math.PI * latHeight))) - (Math.PI / 2);
      latHeight *= (180 / Math.PI);

      lat = (2 * Math.atan(Math.exp(Math.PI * lat))) - (Math.PI / 2);
      lat *= (180 / Math.PI);

      latHeight -= lat;

      if (lonWidth < 0) {
         lon      = lon + lonWidth;
         lonWidth = -lonWidth;
      }

      if (latHeight < 0) {
         lat       = lat + latHeight;
         latHeight = -latHeight;
      }

      //		lat = Math.asin(lat) * 180 / Math.PI;
      return new Rectangle2D.Double(lon, lat, lonWidth, latHeight);
   }

   /**
   * returns a Rectangle2D with x = lon, y = lat, width=lonSpan, height=latSpan
   * for an x,y,zoom as used by google.
   */
   public static Rectangle2D.Double getLatLong(int x, int y, int zoom) {
      double lon      = -180; // x
      double lonWidth = 360; // width 360

      //double lat = -90;  // y
      //double latHeight = 180; // height 180
      double lat       = -1;
      double latHeight = 2;

      int tilesAtThisZoom = 1 << (17 - zoom);
      lonWidth  = 360.0 / tilesAtThisZoom;
      lon       = -180 + (x * lonWidth);
      latHeight = -2.0 / tilesAtThisZoom;
      lat       = 1 + (y * latHeight);

      // convert lat and latHeight to degrees in a transverse mercator projection
      // note that in fact the coordinates go from about -85 to +85 not -90 to 90!
      latHeight += lat;
      latHeight = (2 * Math.atan(Math.exp(Math.PI * latHeight))) - (Math.PI / 2);
      latHeight *= (180 / Math.PI);

      lat = (2 * Math.atan(Math.exp(Math.PI * lat))) - (Math.PI / 2);
      lat *= (180 / Math.PI);

      latHeight -= lat;

      if (lonWidth < 0) {
         lon      = lon + lonWidth;
         lonWidth = -lonWidth;
      }

      if (latHeight < 0) {
         lat       = lat + latHeight;
         latHeight = -latHeight;
      }

      return new Rectangle2D.Double(lon, lat, lonWidth, latHeight);
   }

   /**
    * returns a keyhole string for a longitude (x), latitude (y), and zoom
    */
   public static String getTileRef(double lon, double lat, int zoom) {
      zoom = 18 - zoom;

      // first convert the lat lon to transverse mercator coordintes.
      if (lon > 180) {
         lon -= 360;
      }

      lon /= 180;

      // convert latitude to a range -1..+1
      lat = Math.log(Math.tan((Math.PI / 4) + ((0.5 * Math.PI * lat) / 180))) / Math.PI;

      double tLat      = -1;
      double tLon      = -1;
      double lonWidth  = 2;
      double latHeight = 2;

      StringBuffer keyholeString = new StringBuffer("t");

      for (int i = 0; i < zoom; i++) {
         lonWidth /= 2;
         latHeight /= 2;

         if ((tLat + latHeight) > lat) {
            if ((tLon + lonWidth) > lon) {
               keyholeString.append('t');
            }
            else {
               tLon += lonWidth;
               keyholeString.append('s');
            }
         }
         else {
            tLat += latHeight;

            if ((tLon + lonWidth) > lon) {
               keyholeString.append('q');
            }
            else {
               tLon += lonWidth;
               keyholeString.append('r');
            }
         }
      }

      return keyholeString.toString();
   }

   /** returns the Google zoom level for the keyhole string. */
   public static int getTileZoom(String keyHoleString) {
      return 18 - keyHoleString.length();
   }

   /** Tests */
   public static void main(String[] args) {
      System.out.println(getLatLong(0, 0, 15));
      System.out.println(getLatLong(1, 1, 15));
      System.out.println(getLatLong(2, 2, 15));
      System.out.println(getLatLong(3, 3, 15));
   }
}
